Method and apparatus for improving sidewall coverage during sputtering in a chamber having an inductively coupled plasma

ABSTRACT

Increased sidewall coverage by a sputtered material is achieved by generating an ionizing plasma in a relatively low pressure sputtering gas. By reducing the pressure of the sputtering gas, it is believed that the ionization rate of the deposition material passing through the plasma is correspondingly reduced which in turn is believed to increase the sidewall coverage by the underlayer. Although the ionization rate is decreased, sufficient bottom coverage of the by the material is maintained. In an alternative embodiment, increased sidewall coverage by the material may be achieved even in a high density plasma chamber by generating the high density plasma only during an initial portion of the material deposition. Once good bottom coverage has been achieved, the RF power to the coil generating the high density plasma may be turned off entirely and the remainder of the deposition conducted without the high density plasma. Consequently, it has been found that good sidewall coverage is achieved in the latter part of the deposition.

FIELD OF THE INVENTION

The present invention relates to plasma generators, and moreparticularly, to a method and apparatus for generating a plasma tosputter deposit a layer of material in the fabrication of semiconductordevices.

BACKGROUND OF THE INVENTION

Low pressure radio frequency (RF) generated plasmas have becomeconvenient sources of energetic ions and activated atoms which can beemployed in a variety of semiconductor device fabrication processesincluding surface treatments, depositions, and etching processes. Forexample, to deposit materials onto a semiconductor wafer using a sputterdeposition process, a plasma is produced in the vicinity of a sputtertarget material which is negatively biased. Ions created adjacent thetarget impact the surface of the target to dislodge, i.e., “sputter”material from the target. The sputtered materials are then transportedand deposited on the surface of the semiconductor wafer.

Sputtered material has a tendency to travel in straight line paths, fromthe target to the substrate being deposited, at angles which are obliqueto the surface of the substrate. As a consequence, materials depositedin etched openings including trenches and holes of semiconductor deviceshaving openings with a high depth to width aspect ratio, may notadequately coat the walls of the openings, particularly the bottomwalls. If a large amount of material is being deposited, the depositedmaterial can bridge over causing undesirable cavities in the depositionlayer. To prevent such cavities, sputtered material can be redirectedinto substantially vertical paths between the target and the substrateby negatively biasing (or self biasing) the substrate and positioningappropriate vertically oriented electric fields adjacent the substrateif the sputtered material is sufficiently ionized by the plasma.However, material sputtered by a low density plasma often has anionization degree of less than 10% which is usually insufficient toavoid the formation of an excessive number of cavities. Accordingly, itis desirable to increase the density of the plasma to increase theionization rate of the sputtered material in order to decrease theformation of unwanted cavities in the deposition layer. As used herein,the term “dense plasma” is intended to refer to one that has a highelectron and ion density, in the range of 10¹¹-10¹³ ions/cm³.

There are several known techniques for exciting a plasma with RF fieldsincluding capacitive coupling, inductive coupling and wave heating. In astandard inductively coupled plasma (ICP) generator, RF current passingthrough a coil surrounding the plasma induces electromagnetic currentsin the plasma. These currents heat the conducting plasma by ohmicheating, so that it is sustained in steady state. As shown in U.S. Pat.No. 4,362,632, for example, current through a coil is supplied by an RFgenerator coupled to the coil through an impedance matching network,such that the coil acts as the first windings of a transformer. Theplasma acts as a single turn second winding of a transformer.

Although such techniques can reduce the formation of voids, furtherreduction of void formation is needed.

SUMMARY OF THE PREFERRED EMBODIMENTS

It is an object of the present invention to provide an improved methodand apparatus for generating a plasma within a chamber and for sputterdepositing a layer which enhances both sidewall and bottom coverage.

These and other objects and advantages are achieved by, in accordancewith one aspect of the invention, a plasma generating apparatus in whicha layer of titanium, a titanium compound or other suitable depositionmaterial is deposited in such a manner as to increase the coverage ofsidewalls of channels, vias and other high aspect ratio openings andstructures having a sidewall in a substrate. It has been found that byincreasing the sidewall coverage of underlayers, the flow of aluminum orother overlayer materials into the opening is enhanced so as tosubstantially reduce the formation of voids in the overlayer.

In one embodiment, increased sidewall coverage by an underlayer materialis achieved by generating an ionizing plasma in a relatively lowpressure precursor or sputtering gas. By reducing the pressure of thesputtering gas, it is believed that the ionization rate (or thedirectionality or both) of the underlayer deposition material passingthrough the plasma is correspondingly reduced which in turn is believedto increase the sidewall coverage by the underlayer. Although theionization rate is decreased, sufficient bottom coverage of the channelsby the underlayer material is maintained. Another advantage of reducingthe sputtering gas pressure is that the deposition rate of theunderlayer material may be increased as well.

In an alternative embodiment, increased sidewall coverage by theunderlayer material may be achieved even in a high density plasmachamber by generating the high density plasma only during an initialportion of the underlayer material deposition. It has been found thatgood bottom coverage may be achieved by ionizing the underlayerdeposition material using a high density plasma during the initialportion of the deposition. Once good bottom coverage has been achieved,the RF power to the coil generating the high density plasma may beturned off entirely and the remainder of the underlayer depositionconducted without the high density plasma. It has been found that goodsidewall coverage is then achieved in the latter part of the deposition.Consequently, good overall coverage of the opening is achieved combiningthe bottom coverage of the initial portion of the deposition with thesidewall coverage obtained during the latter portion of the underlayerdeposition.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective, partial cross-sectional view of a plasmagenerating chamber for improving sidewall coverage in a manner inaccordance with an embodiment of the present invention.

FIG. 2 is a schematic diagram of the electrical interconnections to theplasma generating chamber of FIG. 1.

FIG. 3 is a cross-sectional view of an opening having an underlayer ofdeposition material deposited in a high density plasma.

FIG. 4 is a cross-sectional view of the opening of FIG. 3 having aninterconnect layer deposited over the underlayer of FIG. 3.

FIG. 5(a) is a cross-sectional view of an opening deposited with anunderlayer of deposition material in a low pressure plasma in accordancewith the present invention.

FIG. 5(b) is a cross-sectional view of the opening of FIG. 5(a) havingan interconnect layer deposited over the underlayer of FIG. 5(a).

FIG. 6 is a schematic top plan view of a staged-vacuum, multiple chambersemiconductor wafer processing system incorporating the vacuum chamberof FIGS. 1-2.

DETAILED DESCRIPTION OF THE DRAWINGS

Referring first to FIGS. 1-2, an example of a plasma generator used inaccordance with an embodiment of the present invention comprises asubstantially cylindrical plasma chamber 100 which is received in avacuum chamber 102 (FIG. 2). The plasma chamber 100 of this embodimenthas a single helical coil 104 which is carried internally of the vacuumchamber walls by a chamber shield 106. The chamber shield 106 protectsthe interior walls of the vacuum chamber 102 from the material beingdeposited within the interior of the plasma chamber 100.

Radio frequency (RF) energy from an RF generator 300 (FIG. 2) isradiated from the coil 104 into the interior of the plasma chamber 100,which energizes a plasma within the plasma chamber 100. An ion fluxstrikes a negatively biased target 110 positioned above the plasmachamber 100. The plasma ions eject material from the target 110 onto asubstrate 112 which may be a wafer or other workpiece supported by apedestal 114 at the bottom of the plasma chamber 100. An optionalrotating magnet assembly 116 may be provided above the target 110 toproduce magnetic fields which sweep over the face of the target 110 topromote uniform erosion by sputtering of the target 110.

The deposition material sputtered from the target 110 passes through theplasma energized by the coil 104 prior to being deposited on thesubstrate 112. A portion of the deposition material passing though theplasma is ionized by the plasma. The ionized deposition material is thenattracted to a negative potential on the substrate 112. In this manner,the ionized deposition material is redirected to a more vertical pathwhich facilitates depositing more material into high aspect ratioopenings in the substrate.

As will be explained in greater detail below, in accordance with oneaspect of the present invention, the ionization of the depositionmaterial is controlled so as to improve the sidewall coverage ofopenings or other structures having sidewalls while maintaining goodbottom coverage as well. Such an arrangement is particularly useful whendepositing an underlayer for an interconnect layer of a metal such asaluminum. For example, the improved sidewall coverage of the underlayerhas been found to significantly facilitate the flow of aluminum into thechannel, even when the aluminum is not ionized, so as to significantlyreduce the incidence of undesirable voids forming in the aluminum layer.

A deposition process in accordance with the present invention is usefulfor a variety of underlayers including wetting layers, seed layers,nucleation layers and barrier layers formed from a variety of depositionmaterials including aluminum, copper, tungsten, tungsten fluoride,titanium, titanium nitride and tantalum nitride. In addition, anystructure having a sidewall can benefit this process including capacitorelectrodes formed of a number of electrode materials including titaniumand platinum. The process may be used to deposit ferroelectricsincluding BST (barium strontium titanate) and PZT (lead zirconiumtitanate) and conductors including aluminum, copper and gold.

FIG. 2 includes a schematic representation of the electrical connectionsof the plasma generating apparatus of this illustrated embodiment. Tosputter target material onto the substrate 112, the target 110 ispreferably negatively biased by a variable DC power source 302 toattract the ions generated by the plasma. In the same manner, thepedestal 114 may be negatively biased by a variable DC power source 304to bias the substrate 112 negatively to attract the ionized depositionmaterial to the substrate 112. In an alternative embodiment, thepedestal 114 may be biased by a high frequency RF power source to biasthe substrate 112 so as to attract the ionized deposition material moreuniformly to the substrate 112. In yet another alternative embodiment,as set forth in copending application Ser. No. 08/677,588, entitled “AMethod for Providing Full-face High Density Plasma Physical VaporDeposition,” filed Jul. 9, 1996 (Attorney Docket # 1402/PVD/DV) andassigned to the assignee of the present application, an external biasingof the substrate 112 may be omitted.

One end of the coil 104 is coupled to an RF source such as the output ofan amplifier and matching network 306, the input of which is coupled tothe RF generator 300. The other end of the coil 104 is coupled toground, preferably through a capacitor 308, which may be a variablecapacitor.

The coil 104 is carried on the chamber shield 106 by a plurality of coilstandoffs 120 (FIG. 1) which electrically insulate the coil 104 from thesupporting chamber shield 106. In addition, the insulating coilstandoffs 120 have an internal labyrinth structure which permitsrepeated deposition of conductive materials from the target 110 onto thecoil standoffs 120 while preventing the formation of a completeconducting path of deposited material from the coil 104 to the chambershield 106. Such a completed conducting path is undesirable because itcould short the coil 104 to the chamber shield 106 (which is typicallygrounded).

RF power is applied to the coil 104 by feedthrough bolts which aresupported by insulating feedthrough standoffs 124. The feedthroughstandoffs 124, like the coil support standoffs 120, permit repeateddeposition of conductive material from the target onto the feedthroughstandoff 124 without the formation of a conducting path which couldshort the coil 104 to the chamber shield 106. The coil feedthroughstandoff 124, like the coil support standoff 120, has an internallabyrinth structure to prevent the formation of a short between the coil104 and the wall 126 of the shield. The feedthrough is coupled to the RFgenerator 300 (shown schematically in FIG. 2) through the matchingnetwork 306 (also shown schematically in FIG. 2).

As set forth above, the RF power radiated by the coil 104 energizes theplasma in the chamber to ionize the target material being sputtered fromthe target 110. The ionized sputtered target material is in turnattracted to the substrate 112 which is at a negative (DC or RF)potential to attract the ionized deposition material to the substrate112.

FIG. 3 shows in cross section an opening 400 in an oxide layer 402 of asubstrate in which an underlayer 404 of titanium has been deposited. Theopening 400 may be a via, channel or other structure having a sidewallor a narrow cross-sectional width (1 micron or less, for example) and ahigh depth to width aspect ratio. In the example of FIG. 4, the openinghas a width of approximately 0.34 microns and a depth to width aspectratio of approximately 3. Absent ionization, much of the titanium atomsarriving on the surface 406 of the substrate would be at angles toooblique to penetrate very deeply into the opening 400. Consequently, toincrease the amount of material entering the opening 400, titaniumsputtered from the target 110 is preferably ionized by the plasma in thechamber so that the path of travel of at least some of the depositionmaterial is more vertically aligned so as to reach the bottom of theopening 400.

In the deposition of the titanium underlayer 404 of FIG. 4, the pressureof the argon precursor or sputtering gas was approximately 30 mTorr, atypical value for high density plasma sputtering. Although theionization of the titanium at this pressure permits very good bottomcoverage as indicated by the bottom portion 408 of the underlayer 404,it has been found that the resultant sidewall coverage can be very thinas indicated by the side wall portion 410 of the underlayer 404, or evendiscontinuous. It is believed that sidewall coverage this thin hindersthe interaction between the titanium underlayer 404 and the subsequentlydeposited aluminum interconnect layer 412 (FIG. 4) such that voids 414form in the aluminum layer at an undesirable rate.

It has been found that the sidewall coverage of the underlayer may besignificantly improved by generating the ionizing plasma at a pressuresubstantially below the pressures typically used in high density plasmasputterings. FIG. 5(a) shows an opening 500 in an oxide layer 502 of asubstrate in which an underlayer 504 of titanium has been deposited in aplasma generated at an argon sputtering gas pressure of 5 mTorr ratherthan 30 mTorr. As shown in FIG. 5(a), very good bottom coverage asindicated by the bottom portion 508 has been maintained yet the sidewallcoverage has been substantially thickened as indicated by the side wallportion 510 of the underlayer 504. (The relative proportions of theunderlayer 504 are not shown to scale in FIG. 5(a) but are exaggeratedfor purposes of clarity.) This improved sidewall coverage is believed toresult from a decrease in the ionization rate of the titanium by theplasma. Because the plasma is generated in a lower pressure argonsputtering gas, it is believed that fewer argon ions and electrons aregenerated in the plasma such than fewer atoms of the titanium areionized prior to depositing on the substrate. As a consequence, theangle of incidence of the titanium atoms is, on average, more obliquesuch that an increased percentage of the titanium is deposited on thesidewall rather than the bottom of the opening 500. Nonetheless, asufficient amount of the titanium is ionized so as to ensure adequatebottom coverage of the opening 500 as well. It is believed that bothgood sidewall and good bottom coverages may be achieved at othersputtering gas pressures below 30 mTorr including 20 and 10 mTorr.

FIG. 5(b) shows an aluminum interconnect layer 512 deposited onto thetitanium underlayer 504. Because of the improved sidewall coverage ofthe underlayer 504, the aluminum interaction with the titaniumunderlayer 504 is improved such that the opening more frequently fillscompletely without forming a void. Resistances of aluminum interconnectlayers deposited in vias of test wafers in which the underlying titaniumlayers were deposited at pressures of 10 mTorr and 20 mTorr have shownremarkable decreases over those in which the underlying titanium layerswere deposited at 30 mTorr. It is believed that the substantialimprovement in resistance is a result of a substantial reduction in thenumber of voids in the aluminum layer in the vias as a result ofimproved sidewall coverage by the titanium underlayer.

Although the improved process of the illustrated embodiment has beendescribed in connection with a titanium underlayer and an aluminumoverlayer, it should be appreciated that the present invention isapplicable to enhancing sidewall coverage of wetting layers, seed layersand nucleation layers of other types of materials. For example, theprocess may be applied to enhance the sidewall coverage of under layersformed of titanium nitride, tantalum and tantalum nitride for aluminumfill and copper barrier layers. Other applications include enhancing thesidewalls of seed layers of aluminum or copper for subsequentdepositions of nonionized aluminum or copper, respectively. Still otherexamples include improving sidewall coverage of tungsten nucleationlayers as part of a CVD (chemical vapor deposition) process. Furtherstructures which can benefit from the process of the present inventioninclude electrodes of devices such as capacitors and other conductors.

In an alternative embodiment, the underlayer for the overlyinginterconnect layer may be formed in a two-step process in which, in thefirst step, an initial portion of the underlayer is deposited in a highpressure (e.g. 30 mTorr) plasma with RF power being applied to the coil104 at a relatively high level such as 1500 watts, for example. As aresult, the initial portion of the underlayer will look substantiallylike the underlayer depicted in FIG. 3 in which good bottom coverage isachieved but the sidewall coverage is relatively thin. However, beforethe deposition of the underlayer is completed, in a second step, the RFpower to the coil 104 may be substantially reduced or even turned off soas to reduce or eliminate ionization of the material being deposited. Asa consequence the amount of deposition material being deposited onto thesubstrate at oblique angles will be increased after the RF power to thecoil is turned off which will in turn enhance the sidewall coverage ofthe openings in a manner similar to that depicted in FIG. 5(a). In thismanner, the bottoms of the openings are preferentially deposited in thefirst step and the sidewalls are preferentially deposited in the secondstep so as to achieve a good overall coating of both the bottoms andsidewalls forming the underlayer. During the second step, the pressuremay be maintained at the full 30 mTorr level or alternatively, sinceionization of the deposition material is reduced or eliminated, thepressure may be reduced substantially so as to reduce scattering andincrease the deposition rate onto the substrate.

FIG. 6 is a schematic plan view of a staged-vacuum semiconductor waferprocessing system 620 of the type which is described in greater detailin U.S. Pat. No. 5,186,718. The system 620 includes a housing 622 whichdefines four chambers: a robot buffer chamber 624 at one end, a transferrobot chamber 628 at the opposite end, and a pair of intermediateprocessing or treatment chambers 626 and 627. Although one or more loadlock chambers 621 may be used, preferably two or three such chambers aremounted to the buffer chamber and in communication with the interior ofthe buffer robot chamber via access ports 636 and associated slit valves638. A plurality of vacuum processing chambers 634 (including thechamber 100 described above) are mounted about the periphery of thetransfer robot station. The chambers 634 may be adapted for varioustypes of processing including etching and/or deposition. Access isprovided to and between each of the chambers by an associated port 636and gate valve 638.

The robot chambers 624 and 628 communicate with one another via theintermediate processing or treatment chambers 626 and 627 (also called“treatment” chambers). Specifically, intermediate treatment chamber 626is located along a corridor or pathway 630 which connects the transferrobot chamber 628 to the buffer robot chamber 624. Similarly, the secondintermediate treatment chamber 627 is located along a separate corridoror pathway 632 which connects the robots 628 and 624. These separatepaths between the two robot or transfer chambers permit one path to beused for loading or unloading while the system is being used for waferprocessing treatment and, thus, provide increased throughput. Thechambers 626 and 627 can be dedicated to pre-treating (e.g., plasma etchcleaning and/or heating) of the wafers before processing in chambers 634or post-treating (e.g., cool-down) of the wafers following treatment inchambers 634; alternatively, one or both of the chambers 626 and 627 canbe adapted for both pre-treatment and post-treatment.

Preferably, the housing 622 is a monolith, i.e., it is machined orotherwise fabricated of one piece of material such as aluminum to formthe four chamber cavities 624, 626, 627 and 628 and the interconnectingcorridors or pathways 630 and 632. The use of the monolith constructionfacilitates alignment of the individual chambers for wafer transport andalso eliminates difficulties in sealing the individual chambers.

One typical operational cycle of wafer transport through the system 20is as follows. Initially, an R THETA buffer robot 640 in chamber 624picks up a wafer from a cassette load lock 621 and transports the waferto chamber 626 which illustratively etch cleans the surface of thewafer. R THETA transfer robot 642 in chamber 628 picks up the wafer fromthe pre-cleaning chamber 626 and transfers the wafer to a selected oneof the preferably high vacuum processing chambers 634. One of thesechambers is the chamber 100 which deposits an underlayer of titanium orother suitable material as set forth above. Following processing,transfer robot 642 can transfer the wafer selectively to one or more ofthe other chambers 634 for processing. Included amongst these chambersis a deposition chamber which deposits aluminum or other suitableinterconnect material on the underlayer previously deposited in thechamber 100. Because the underlayer has good sidewall as well as bottomcoverage, the chamber depositing the aluminum may be a conventionalmagnetron sputtering chamber which does not have an RF coil to produce ahigh density plasma to ionize the aluminum. Instead, the aluminum may bedeposited without being ionized yet can form an interconnect layerhaving a relatively low resistance with few or no voids in the openings.Upon completion of depositions and etchings, the transfer robot 642transfers the wafer to intermediate processing chamber 627 whichillustratively is a cool-down chamber. After the cool-down cycle, bufferrobot 640 retrieves the wafer from the chamber 627 and returns it to theappropriate cassette load lock chamber 621.

The buffer robot 640 may be any suitable robot such as the dual four-barlink robot disclosed in allowed Maydan et. al. patent application,entitled “Multi-Chamber Integrated Process System”, U.S. applicationSer. No. 283,015, now abandoned, which application is incorporated byreference. The transfer robot 642 likewise may be any suitable robotsuch as the robot described in the aforementioned U.S. Pat. No.5,186,718.

The control functions described above for the system 600 including thecontrol of power to the RF coils, targets and substrates, robot control,chamber venting and pumping control, and cassette indexing arepreferably provided by a workstation (not shown) programmed to controlthese system elements in accordance with the above description.

In each of the embodiments discussed above, a multiple turn coil 104 wasused, but, of course, a single turn coil may be used instead. Stillfurther, instead of the ribbon shape coil 104 illustrated, each turn ofthe coil 104 may be implemented with a flat, open-ended annular ring asdescribed in copending application Ser. No. 08/680,335, entitled “Coilsfor Generating a Plasma and for Sputtering,” filed Jul. 10, 1996(Attorney Docket # 1390-CIP/PVD/DV) and assigned to the assignee of thepresent application, which application is incorporated herein byreference in its entirety.

Each of the embodiments discussed above utilized a single coil in theplasma chamber. It should be recognized that the present invention isapplicable to plasma chambers having more than one RF powered coil or RFpowered shields. For example, the present invention may be applied tomultiple coil chambers for launching helicon waves of the type describedin aforementioned copending application Ser. No. 08/559,345, filed Nov.15, 1995 and entitled “Method And Apparatus For Launching a Helicon Wavein a Plasma” (Atty Docket No. 938).

The appropriate RF generators and matching circuits are components wellknown to those skilled in the art. For example, an RF generator such asthe ENI Genesis series which has the capability to “frequency hunt” forthe best frequency match with the matching circuit and antenna issuitable. The frequency of the generator for generating the RF power tothe coil 104 is preferably 2 MHz but it is anticipated that the rangecan vary from, for example, 1 MHz to 4 MHz. An RF power setting of 1.5kW is preferred but a range of 1.5-5 kW is satisfactory. In addition, aDC power setting for biasing the target 110 of 5 kW is preferred but arange of 2-10 kW and a pedestal 114 bias voltage of −30 volts DC issatisfactory.

A variety of sputtering gases may be utilized to generate the plasmaincluding Ar, H₂, O₂ or reactive gases such as NF₃, CF₄ and many others.Various sputtering gas pressures are suitable including pressures of0.1-50 mTorr. For ionized PVD, a pressure between 10 and 100 mTorr ispreferred for best ionization of sputtered material.

It will, of course, be understood that modifications of the presentinvention, in its various aspects, will be apparent to those skilled inthe art, some being apparent only after study, others being matters ofroutine mechanical and electronic design. Other embodiments are alsopossible, their specific designs depending upon the particularapplication. As such, the scope of the invention should not be limitedby the particular embodiments herein described but should be definedonly by the appended claims and equivalents thereof.

1. A process for sputter depositing a layer of material into a workpiecestructure having a sidewall, comprising: providing a sputtering gas intoa chamber at a pressure below 20 mTorr; applying RF power to a coil toionize the sputtering gas to form a plasma; sputtering a target tosputter target material toward a workpiece; and ionizing a portion ofsaid sputtered target material before it is deposited onto saidworkpiece.
 2. The process of claim 1 wherein said sputtering gas is at apressure of 5-10 mTorr.
 3. The process of claim 1 wherein said targetmaterial is selected from the group of titanium, tantalum, aluminum,copper and tungsten.
 4. The process of claim 3 wherein said targetmaterial is a compound of nitrogen and a material selected from thegroup of tantalum and titanium.
 5. A process for sputter depositing alayer of material into a via or channel of a workpiece, comprising:providing a sputtering gas into a chamber; applying RF power to a coilto ionize the sputtering gas to form a plasma; sputtering a target tosputter target material toward a workpiece; ionizing a portion of saidsputtered target material before it is deposited onto said workpiece;reducing said RF power to said coil while continuing to sputter saidtarget so as to reduce ionization of said sputtered target materialbefore it is deposited onto said workpiece.
 6. The process of claim 5wherein said RF power reducing step reduces said RF power to zero.
 7. Aprocess for sputter depositing a layer of material into an opening of aworkpiece, said opening having a bottom and sidewalls, said processcomprising: sputtering a target to sputter target material toward aworkpiece; ionizing a portion of said sputtered target material beforeit is deposited onto said workpiece so that sputtered material which isdeposited in said opening is deposited primarily on the bottom of saidopening; and reducing said ionizing of sputtered material so thatsputtered material deposited in said opening is deposited primarily onthe sidewalls of said opening.
 8. The process of claim 7 wherein saidionizing reducing step reduces ionization of sputtered material to zero.9. The process of claim 7 wherein said sputtering gas is at a pressureof 5-10 mTorr.
 10. The process of claim 7 wherein said target materialis selected from the group of titanium, tantalum, aluminum, copper andtungsten.
 11. A process for sputter depositing layers of materials intoa workpiece structure having a sidewall and a bottom, comprising:sputtering a first target in a first chamber to sputter target materialtoward a workpiece; ionizing a portion of said sputtered first targetmaterial before it is deposited onto said workpiece so that sputteredmaterial which is deposited on said structure is deposited primarily onthe bottom of said structure; and reducing said ionizing of saidsputtered first target material so that sputtered first target materialdeposited on said structure is deposited primarily on the sidewalls ofsaid structure; transferring said workpiece to a second chamber;sputtering a second target to sputter a second target material onto saidstructure of said workpiece to deposit on top of said first materialdeposited on said structure.
 12. The process of claim 11 wherein saidsputtering gas is at a pressure of 5-10 mTorr.
 13. The process of claim11 wherein said first target material is selected from the group oftitanium, tantalum, aluminum, copper and tungsten.
 14. The process ofclaim 11 wherein said second target material is selected from the groupof aluminum and copper.
 15. A process for sputter depositing layers ofmaterials into a via or channel of a workpiece, comprising: providing asputtering gas into a first chamber at a pressure below 20 mTorr;applying RF power to a coil in said first chamber to ionize saidsputtering gas to form a plasma; sputtering a target to sputter a firsttarget material toward a workpiece; ionizing a portion of said sputteredtarget material before it is deposited onto said workpiece; transferringsaid workpiece to a second chamber; sputtering a second target tosputter a second target material toward said workpiece.
 16. The processof claim 15 wherein said sputtering gas is at a pressure of 5-10 mTorr.17. The process of claim 15 wherein said first target material isselected from the group of titanium, tantalum, aluminum, copper andtungsten.
 18. The process of claim 15 wherein said second targetmaterial is selected from the group of aluminum and copper.
 19. Anapparatus for energizing a plasma within a semiconductor fabricationsystem to sputter material onto a workpiece, the apparatus comprising: asemiconductor fabrication chamber having a plasma generation area withinsaid chamber and containing a sputtering gas at a pressure less than 25mTorr; and a coil carried by said chamber and positioned to coupleenergy into said plasma generation area.
 20. The apparatus of claim 19including a target including is a target material selected from thegroup of titanium, tantalum, aluminum, copper and tungsten.
 21. Asemiconductor fabrication system for sputtering multiple layers ofmaterials onto a workpiece, the system comprising: a first semiconductorfabrication chamber having a plasma generation area within said chamberand containing a sputtering gas at a pressure less than 25 mTorr; saidfirst chamber having a target of a first target material which includesa material selected from the group of titanium, tantalum, aluminum,copper and tungsten; a coil carried by said first chamber and positionedto couple energy into said plasma generation area to ionize said firsttarget material to form an underlayer of said first material on saidworkpiece; a second semiconductor fabrication chamber; and said secondchamber having a second target of a second target material whichincludes a material selected from the group of aluminum and copper, forforming a layer on said underlayer.
 22. An apparatus for energizing aplasma within a semiconductor fabrication system to sputter materialonto a workpiece, the apparatus comprising: a semiconductor fabricationchamber having a plasma generation area within said chamber; a coilcarried by said chamber and positioned to couple energy into said plasmageneration area to ionize said material prior to deposition onto saidworkpiece; an RF generator coupled to said coil to provide RF power tosaid coil; and control means for controlling said RF generator toprovide power at a high level during an initial portion of a sputterdeposition and to provide power at a reduced level including zero powerin a subsequent portion of said sputter deposition.
 23. The apparatus ofclaim 22 including a target including a material selected from the groupof titanium, tantalum, aluminum, copper and tungsten.
 24. Asemiconductor fabrication system for sputtering multiple layers ofmaterials onto a workpiece, the system comprising: a first semiconductorfabrication chamber having a plasma generation area within said chamberand a target of a first target material which includes a materialselected from the group of titanium, tantalum, aluminum, copper andtungsten; a coil carried by said chamber and positioned to couple energyinto said plasma generation area to ionize said first target materialprior to deposition onto said workpiece; an RF generator coupled to saidcoil to provide RF power to said coil; and control means for controllingsaid RF generator to provide power at a high level during an initialportion of a sputter deposition and to provide power at a reduced levelincluding zero power in a subsequent portion of said sputter deposition;a second semiconductor fabrication chamber; and said second chamberhaving a second target of a second target material which includes is amaterial selected from the group of aluminum and copper, for forming alayer on said underlayer.